Hot-gas reciprocating engine



Nov. 25, 1952 KOQPMANS 2,618,923

HOT-GAS RECIPROCATING ENGINE Filed April 12, 1950 INVENTOR.

ADRIAAN KOOPMANS AGENT Patented Nov. 25, 1952 HOT-GAS REGIPB ENGINEAdriaan Koopmans, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn, astrustee Application April 12, 1950, Serial No. 155,450-

In the Netherlands May 14, 1949 4 Claims.

The invention relates to hot-gas reciprocating engines.

According to the invention a hot-gas reciprocating engine comprising aheater which surrounds the hot space at least in part, is characterisedin that, while parts of the wall of the hot space of the engine areexposed at one side to the action of the combustion gases of the heaterthey are cooled by a supply of working medium flowing along the otherside of these parts of the wall directly between the hot space and theregenerator, this supply being small compared with the supply of workingmedium which flows between the hot space and the regenerator by way ofthe heater of the engine.

In a hot-gas engine, heat energy is supplied to the engine by thecombustion gases of a burner. These combustion gases flow through thechannels of a heat exchanger and the working medium through otherchannels of the heat exchanger, the heat transfer between the combustiongases and the working medium taking place through the walls by which thetwo channel systems are separated. A heater of construction hithertoknown generally comprises a wall or parts of a wall which constitute aboundary between the hot space of the engine and the space for thecombustion gases, which in some cases is or are in thermal contact withthe combustion gases. It is true that working medium will generally beavailable on one side of the wall or parts of the wall but, since thevelocity of flow of the working medium along this wall or these parts issmall relative to the velocity of the working medium in the channelsystem of the heater, the heat transfer through this wall or these partswill be relatively small, so that in general there is a risk ofexcessive heating of this wall or these parts.

In a hot-gas reciprocating engine according to the invention part of theworking medium does not pass through the usual channel system to andfrom the heat exchanger but through a second channel system along theone side of the wall or parts of the wall, the other side of which areexposed to the risk of excessive heating. This ensures firstly that thewall is cooled and secondly that the supply of working medium flowingthrough the heater is less than with the constructions in which workingmedium is not used for cooling the wall or parts of the wall. The heatermay consequently be of smaller size. If an adequate passage of thechannels through which the working medium flows, cooling the wall of thehot space, is chosen, this cooling medium may be exposed to the sametemperature differences to which the other part of :-v working mediumflowing through the usual The hot-gas reciprocating engine according to,

the invention may advantageously comprise a heater of which the channelsfor the working medium are constituted by hairpin-shaped pipesv In thiscase the top and the entire side wallof the engine head is generallysubjected to the high temperature combustion gases It is therefore inthis case particularly important to cool the engine head. This coolingmay be effected if an annular space for the working medium is providedbetween the bushing in which the displaced piston is adapted to move andthe wallv of the engine head, said space communicating directly with theregenerator and with the hot space.

In order that the invention may be more clearly understood and readilycarried into effect, it will now be described more fully with referenceto the accompanying diagrammatic drawing which shows one embodiment of ahot-gas engine according thereto, in which the heater compriseshairpin-shaped pipes.

Referring now to the drawing, a displacer 2 is adapted to reciprocate ina cylindrical bushing l. The space above the displacer 2 is the hotspace 3 of the hot-gas engine. Most of the working medium flows betweenthe cold space 4, the volume of which is determined by a piston 5, andthe displacer 2, and the hot space 3 through a cooler 6, a regenerator Iand a heater 8. A smaller amount of the working medium flows through theannular channel 9 directly between the regenerator and the hot space.Above the engine head 13 is provided a burner 10, of which thecombustion gases flow between the groups of pipes of the heater 8. Thisheater is constructed in the form of two groups of hairpin-shaped pipesarranged to surround the combustion space II. The combustion gases,after passing between the pipes, leave the heater at l2, and also flowaround the top and side wall of the engine head l3. A risk of excessiveheating of the engine head I3 is thus incurred.

However, since part of the working medium flows through the annularchannel 9 to the hot space, this risk is mitigated. The amount ofworking medium, flowing directly between the hot space and theregenerator, necessary for cooling purposes, varies with thetemperatures of the hot and cold spaces,

It will be obvious that the invention, which provides cooling of thewall of the hot space, may be used with other heater constructions.

What I claim is:

1. A hot gas engine comprising a cylinder enclosing a hot and cold spacetherein, a displacer in said cylinder separating said hot from said coldspace, means connecting said hot and cold spaces, said means comprisinga heater disposed around one side of the wall of said cylinder adjacentsaid hot space, a regenerator, and a cooler disposed about the cylinderadjacent said cold space, means also directly connecting saidregenerator and said. hot space, said latter means being disposed alongthe other side of the wall of the cylinder adjacent said hot space forthe flow of a relatively small amount of working medium therethrough tocool said wall.

2. A hot gas engine comprising a cylinder enclosing a hot and cold spacetherein, a bushing within said cylinder and spaced from the wall of saidcylinder in the hotspace thereof, a displacer within said cylinderbushing separating said hot from said cold space,'means connecting saidhot and cold spaces, said means comprising a heater disposed around oneside of the wall of said cylinder adjacent said hot space, aregenerator, and a cooler disposed about the cylinder adjacent said coldspace, duct means also directly connecting said regenerator and said hotspace, said duct means being formed between the other side of wall ofthe cylinder adjacent said hot space and the outer periphery of saidbushing for the flow of a relatively small amount of working mediumtherethrough to cool said wall.

3. A hot gas engine comprising a cylinder enclosing a hot and cold spacetherein, a displacer in said cylinder separating said hot from said coldspace, means connecting said hot and cold spaces, said means comprisinga heater formed by hairpin-shaped pipes disposed around one side of thewall of said cylinder adjacent said hot space, a regenerator, and acooler disposed about the cylinder adjacent said cold space, means alsodirectly connecting said regenerator and said hot space, said lattermeans being disposed along the other side of the wall of the cylinderadjacent said hot space for the flow of a relatively small amount ofworking medium therethrough to cool said Wall.

4. A hot gas engine comprising a cylinder enclosing a hot and cold spacetherein, a cylindrical bushing within the hot space part of saidcylinder and spaced therefrom throughout part of its length to form anannular space between the wall of said cylinder and said bushing, adisplacer within said cylinder and bushing separating said hot from saidcold space, means connecting said hot and cold spaces, said meanscomprising a heater disposed around the outer periphery of the wall ofsaid cylinder adjacent said hot space, a regenerator, and a coolerdisposed about the cylinder adjacent said cold space, said annular spacealso directly connecting said regenerator and said hot space for theflow of a relatively small amount 'of working medium therethrough tocool said wall.

ADRIAAN KO'OPMANS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

